Experimental relativistic zero-knowledge proofs

Protecting secrets is a key challenge in our contemporary information-based era. In common situations, however, revealing secrets appears unavoidable, for instance, when identifying oneself in a bank to retrieve money. In turn, this may have highly undesirable consequences in the unlikely, yet not unrealistic, case where the bank's security gets compromised. This naturally raises the question of whether disclosing secrets is fundamentally necessary for identifying oneself, or more generally for proving a statement to be correct. Developments in computer science provide an elegant solution via the concept of zero-knowledge proofs: a prover can convince a verifier of the validity of a certain statement without facilitating the elaboration of a proof at all. In this work, we report the experimental realisation of such a zero-knowledge protocol involving two separated verifier-prover pairs. Security is enforced via the physical principle of special relativity, and no computational assumption (such as the existence of one-way functions) is required. Our implementation exclusively relies on off-the-shelf equipment and works at both short (60 m) and long distances (400 m) in about one second. This demonstrates the practical potential of multi-prover zero-knowledge protocols, promising for identification tasks and blockchain-based applications such as cryptocurrencies or smart contracts.Comment: 8 pages, 3 figure

Fast Single Photon Detectors and real-time Key Distillation: Enabling High Secret Key Rate QKD Systems

Quantum Key Distribution has made continuous progress over the last 20 years and is now commercially available. However, the secret key rates (SKR) are still limited to a few Mbps. Here, we present a custom multipixel superconducting nanowire single-photon detectors and fast acquisition and real-time key distillation electronics, removing two roadblocks and allowing an increase of the SKR of more than an order of magnitude. In combination with a simple 2.5 GHz clocked time-bin quantum key distribution system, we can generate secret keys at a rate of 64 Mbps over a distance of 10.0 km and at a rate of 3.0 Mbps over a distance of 102.4 km with real-time key distillation.Comment: 5 pages, 5 figures, submitted to Nature Photonic

Assessing the dynamics of organic aerosols over the North Atlantic Ocean

© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 7 (2017): 45476, doi:10.1038/srep45476.The influence of aerosols on climate is highly dependent on the particle size distribution, concentration, and composition. In particular, the latter influences their ability to act as cloud condensation nuclei, whereby they impact cloud coverage and precipitation. Here, we simultaneously measured the concentration of aerosols from sea spray over the North Atlantic on board the exhaust-free solar-powered vessel “PlanetSolar”, and the sea surface physico-chemical parameters. We identified organic-bearing particles based on individual particle fluorescence spectra. Organic-bearing aerosols display specific spatio-temporal distributions as compared to total aerosols. We propose an empirical parameterization of the organic-bearing particle concentration, with a dependence on water salinity and sea-surface temperature only. We also show that a very rich mixture of organic aerosols is emitted from the sea surface. Such data will certainly contribute to providing further insight into the influence of aerosols on cloud formation, and be used as input for the improved modeling of aerosols and their role in global climate processes.We gratefully acknowledge the financial support by the H. Dudley Wright and the Henri Moser Foundations, the Rector’s Office and the Institute for Environmental Sciences at the University of Geneva, as well as a generous anonymous donator

ARC: pompes a chaleur chimiques

SIGLECNRS RP 440 (316) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

An FPGA-Based 4 Mbps Secret Key Distillation Engine for Quantum Key Distribution Systems

Quantum key distribution (QKD) enables provably secure communication between two parties over an optical fiber that arguably withstands any form of attack. Besides the need for a suitable physical signalling scheme and the corresponding devices, QKD also requires a secret key distillation protocol. This protocol and the involved signal processing handle the reliable key agreement process over the fragile quantum channel, as well as the necessary post-processing of key bits to avoid leakage of secret key information to an eavesdropper. In this paper we present in detail an implementation of a key distillation engine for a QKD system based on the coherent one-way (COW) protocol. The processing of key bits by the key distillation engine includes agreement on quantum bit detections (sifting), information reconciliation with forward error correction coding, parameter estimation, and privacy amplification over an authenticated channel. We detail the system architecture combining all these processing steps, and discuss the design trade-offs for each individual system module. We also assess the performance and efficiency of our key distillation implementation in terms of throughput, error correction capabilities, and resource utilization. On a single-FPGA (Xilinx Virtex-6 LX240T) platform, the system supports distilled key rates of up to 4 Mbps

Practical Relativistic Bit Commitment

Bit commitment is a fundamental cryptographic primitive in which Alice wishes to commit a secret bit to Bob. Perfectly secure bit commitment between two mistrustful parties is impossible through an asynchronous exchange of quantum information. Perfect security is, however, possible when Alice and Bob each split into several agents exchanging classical information at times and locations suitably chosen to satisfy specific relativistic constraints. In this Letter we first revisit a previously proposed scheme [C. Crépeau et al., Lect. Notes Comput. Sci. 7073, 407 (2011)] that realizes bit commitment using only classical communication. We prove that the protocol is secure against quantum adversaries for a duration limited by the light-speed communication time between the locations of the agents. We then propose a novel multiround scheme based on finite-field arithmetic that extends the commitment time beyond this limit, and we prove its security against classical attacks. Finally, we present an implementation of these protocols using dedicated hardware and we demonstrate a 2 ms-long bit commitment over a distance of 131 km. By positioning the agents on antipodal points on the surface of Earth, the commitment time could possibly be extended to 212 ms

Experimental relativistic zero-knowledge proofs

Protecting secrets is a key challenge in our contemporary information-based era. In common situations, however, revealing secrets appears unavoidable, for instance, when identifying oneself in a bank to retrieve money. In turn, this may have highly undesirable consequences in the unlikely, yet not unrealistic, case where the bank's security gets compromised. This naturally raises the question of whether disclosing secrets is fundamentally necessary for identifying oneself, or more generally for proving a statement to be correct. Developments in computer science provide an elegant solution via the concept of zero-knowledge proofs: a prover can convince a verifier of the validity of a certain statement without facilitating the elaboration of a proof at all. In this work, we report the experimental realisation of such a zero-knowledge protocol involving two separated verifier-prover pairs. Security is enforced via the physical principle of special relativity, and no computational assumption (such as the existence of one-way functions) is required. Our implementation exclusively relies on off-the-shelf equipment and works at both short (60 m) and long distances (400 m) in about one second. This demonstrates the practical potential of multi-prover zero-knowledge protocols, promising for identification tasks and blockchain-based applications such as cryptocurrencies or smart contracts

A fast and versatile quantum key distribution system with hardware key distillation and wavelength multiplexing

We present a compactly integrated, 625 MHz clocked coherent one-way quantum key distribution system which continuously distributes secret keys over an optical fibre link. To support high secret key rates, we implemented a fast hardware key distillation engine which allows for key distillation rates up to 4 Mbps in real time. The system employs wavelength multiplexing in order to run over only a single optical fibre. Using fast gated InGaAs single photon detectors, we reliably distribute secret keys with a rate above 21 kbps over 25 km of optical fibre. We optimized the system considering a security analysis that respects finite-key-size effects, authentication costs and system errors for a security parameter of εQKD = 4 × 10−9